The proposed research is designed to characterize the precise pathology of the peripheral degeneration of the retina in Fischer rats, and to study the pathogenesis and etiology of this retinal disease. In addition, this research would also provide useful information concerning the aging processes and the interaction between the age-related and light-associated factors in the retinal tissues. This research is divided into four conceptual areas: The first is to characterize the pathology of the disease temporally, spatially and ultrastructurally, and to determine the effects of age, sex and light on the disease processes. The second is to determine whether or not the retinal vasculature in affected retinas is involved in pathogenesis of the disease. The third is to study the role of outward movement of the photoreceptor cells in the formation of peripheral retinal degeneration. The fourth is to clarify the relationship between the structure changes of the retinal pigment epithelium, and the formation of peripheral retinal degeneration.